FORMING RANGE MAPS USING PERIODIC ILLUMINATION PATTERNS

1 . A method for determining a range map for a scene using a digital camera, comprising:

using a projector to project a sequence of different binary illumination patterns onto a scene from a projection direction;

capturing a sequence of binary pattern images of the scene using the digital camera from a capture direction different from the projection direction, each digital image corresponding to one of the projected binary illumination patterns;

using a projector to project a sequence of periodic grayscale illumination patterns onto the scene from the projection direction, each periodic grayscale pattern having the same frequency and a different phase, the phase of the grayscale illumination patterns each having a known relationship to the binary illumination patterns;

capturing a sequence of grayscale pattern images of the scene using the digital camera from the capture direction, each digital image corresponding to one of the projected periodic grayscale illumination patterns;

wherein the projected binary illumination patterns and periodic grayscale illumination patterns share a common coordinate system having a projected x coordinate and a projected y coordinate, the projected binary illumination patterns and periodic grayscale illumination patterns varying with the projected x coordinate and being constant with the projected y coordinate;

analyzing the sequence of captured binary pattern images to determine coarse projected x coordinate estimates for a set of image locations;

analyzing the sequence of captured grayscale pattern images to determine refined projected x coordinate estimates for the set of image locations responsive to the determined coarse projected x coordinate estimates;

determining range values for the set of image locations responsive to the refined projected x coordinate estimates, wherein a range value is a distance between a reference location and a location in the scene corresponding to an image location;

forming a range map according to the refined range value estimates, the range map comprising range values for an array of image locations, the array of image locations being addressed by two-dimensional image coordinates; and

storing the range map in a processor-accessible memory system.

2 . The method of claim 1 wherein the binary illumination patterns are Gray code patterns.

3 . The method of claim 1 wherein the periodic grayscale illumination patterns are sinusoidal waveforms or triangular waveforms.

4 . The method of claim 1 wherein the sequence of binary illumination patterns define a set of projected image regions of width w p that can be identified by analyzing the sequence of binary pattern images, and wherein the periodic grayscale illumination patterns have a period equal to the width w p .

5 . The method of claim 4 wherein a zero phase position for one of the periodic grayscale illumination patterns is aligned with boundaries between the projected image regions.

6 . The method of claim 4 wherein the sequence of captured binary pattern images are analyzed to associate the locations in the scene with one of the projected image regions to provide the coarse projected x coordinate estimates.

7 . The method of claim 6 wherein the coarse projected x coordinate estimates are represented by indices identifying the associated projected image regions.

8 . The method of claim 6 wherein the refined projected x coordinate estimates are determined by analyzing the captured grayscale pattern images to determine a relative location within the associated projected image region.

9 . The method of claim 8 wherein the refined projected x coordinate estimates are determined by analyzing the captured grayscale pattern images to determine a phase value, and wherein the phase value is used to determine the relative location within the associated projected image region.

10 . The method of claim 8 wherein the range values are determined by using a range function which relates an image location and a corresponding projected x coordinate to a corresponding range value, the range function being determined according to the relative positions of the projector and the digital camera.

11 . The method of claim 1 further including the step of forming a three-dimensional model of the scene responsive to the range map.

12 . The method of claim 11 wherein the range values in the range map are combined with the corresponding two-dimensional image coordinates to provide three-dimensional coordinates for the three-dimensional model.

13 . The method of claim 11 wherein color values for the three-dimensional model are determined by capturing a full color image of the scene using the digital camera.

14 . The method of claim 11 further including combining three-dimensional models determined using digital cameras positioned at different capture directions to determine a combined three-dimensional model.

15 . A system comprising:

a projection system for projecting illumination patterns onto a scene from a projection direction;

a digital camera having an associated capture direction, the capture direction being different from the projection direction;

a data processing system;

a processor-accessible memory system communicatively connected to the data processing system; and

a program memory system communicatively connected to the data processing system and storing instructions configured to cause the data processing system to implement a method for determining a range map, wherein the instructions comprise:

using the projection system to project a sequence of different binary illumination patterns onto a scene;

capturing a sequence of binary pattern images of the scene using the digital camera, each digital image corresponding to one of the projected binary illumination patterns;

using the projection system to project a sequence of periodic grayscale illumination patterns onto the scene from the projection direction, each periodic grayscale pattern having the same frequency and a different phase, the phase of the grayscale illumination patterns having a known relationship to the binary illumination patterns;

capturing a sequence of grayscale pattern images of the scene using the digital camera, each digital image corresponding to one of the projected periodic grayscale illumination patterns;

wherein the projected binary illumination patterns and periodic grayscale illumination patterns share a common coordinate system having a projected x coordinate and a projected y coordinate, the projected binary illumination patterns and periodic grayscale illumination patterns varying with the projected x coordinate and being constant with the projected y coordinate;

analyzing the sequence of captured binary pattern images to determine coarse projected x coordinate estimates for a set of image locations,

analyzing the sequence of captured grayscale pattern images to determine refined projected x coordinate estimates for the set of image locations responsive to the determined coarse projected x coordinate estimates;

determining range values for the set of image locations responsive to the refined projected x coordinate estimates, wherein a range value is a distance between a reference location and a location in the scene corresponding to an image location;

forming a range map according to the refined range value estimates, the range map comprising range values for an array of image locations, the array of image locations being addressed by two-dimensional image coordinates; and

storing the range map in the processor-accessible memory system.

16 . A computer program product for determining a range map for a scene comprising a non-transitory tangible computer readable storage medium storing an executable software application for causing a data processing system to perform the steps of:

using a projector to project a sequence of different binary illumination patterns onto a scene from a projection direction;

capturing a sequence of binary pattern images of the scene using the digital camera from a capture direction different from the projection direction, each digital image corresponding to one of the projected binary illumination patterns;

using a projector to project a sequence of periodic grayscale illumination patterns onto the scene from the projection direction, each periodic grayscale pattern having the same frequency and a different phase, the phase of the grayscale illumination patterns having a known relationship to the binary illumination patterns;

wherein the projected binary illumination patterns and periodic grayscale illumination patterns share a common coordinate system having a projected x coordinate and a projected y coordinate, the projected binary illumination patterns and periodic grayscale illumination patterns varying with the projected x coordinate and being constant with the projected y coordinate;

capturing a sequence of grayscale pattern images of the scene using the digital camera from the capture direction, each digital image corresponding to one of the projected periodic grayscale illumination patterns;

analyzing the sequence of captured binary pattern images to determine coarse projected x coordinate estimates for a set of image locations,

analyzing the sequence of captured grayscale pattern images to determine refined projected x coordinate estimates for the set of image locations responsive to the determined coarse projected x coordinate estimates;

determining range values for the set of image locations responsive to the refined projected x coordinate estimates, wherein a range value is a distance between a reference location and a location in the scene corresponding to an image location;

forming a range map according to the refined range value estimates, the range map comprising range values for an array of image locations, the array of image locations being addressed by two-dimensional image coordinates; and

storing the range map in a processor-accessible memory system.