Stabilization of three-dimensional images in a scannerless range imaging system

1. A method for generating a stabilized three-dimensional image from a scannerless range imaging system of the type comprising an illuminator for illuminating a scene with modulated illumination; an image modulating component for receiving and modulating the modulated illumination reflected from the scene; an image capture element for capturing images output by the image modulating component, including a bundle of at least three phase offset images each incorporating a phase delay corresponding to the distance of objects in the scene from the illuminator, wherein each phase offset image also incorporates a phase offset unique for each image, said method comprising the steps of:

acquiring a bundle of three or more phase offset images corresponding to the modulated illumination reflected from the scene, whereby one or more of the phase offset images includes image motion relative to another phase offset image;

searching for a stable chain of phase offset images in the image bundle, wherein a stable chain is a collection of images that is obtained by testing the phase offset images against a confidence measure that separates less severe correctable image motion from more severe image motion and then populating the stable chain only with those phase offset images that meet the confidence measure for correctable image motion;

correcting for the image motion in the stable chain of images if a stable chain of at least three phase offset images is found to exist; and

computing a stabilized three-dimensional image using corrected phase offset images from the stable chain of phase offset images.

2. The method as claimed in claim 1 wherein the motion between the phase offset images may be either global motion of all objects or localized motion between objects in consecutive images.

3. The method as claimed in claim 2 wherein the stable chain is found to exist between phase offset images exhibiting global motion.

4. The method as claimed in claim 2 wherein the stable chain is found to exist between phase offset images exhibiting local motion.

5. The method as claimed in claim 1 wherein the confidence measure employed in the step of searching for a stable chain of phase offset images comprises testing ordered pairs of phase offset images in the bundle against a phase correlation threshold.

6. The method as claimed in claim 1 wherein the step of searching for a stable chain of phase offset images further comprises collecting two or more ordered pairs that meet the confidence measure in a connected list, where a connected list is defined as a set of at least two ordered pairs (x 1 ,y 1 ) and (x 2 ,y 2 ) in the list satisfying y 1 =x 2 and x 1 ≠y 2 .

7. The method as claimed in claim 1 wherein the step of searching for a stable chain of phase offset images further comprises the step of requiring an image bundle if a stable chain of at least three phase offset images does not exist.

8. A method for generating a stabilized three-dimensional image from a scannerless range imaging system of the type comprising an illuminator for illuminating a scene with modulated illumination; an image modulating component for receiving and modulating the modulated illumination reflected from the scene; an image capture element for capturing images output by the image modulating component, including a bundle of at least three phase offset images each incorporating a phase delay corresponding to the distance of objects in the scene from the illuminator, wherein each phase offset image also incorporates a phase offset unique for each image, said method comprising the steps of:

acquiring a bundle of three or more phase offset images corresponding to the reflected modulated illumination, whereby one or more of the phase offset images may be subject to movement with respect to another phase offset image;

choosing a motion model for estimating movement between the images;

searching for a stable chain of phase offset images in the image bundle, where a stable chain is a collection of images that is found to exist where the motion model reveals a correlation between the images indicative of correctable global motion;

correcting for the global motion in the stable chain of images if a stable chain of at least three phase offset images is found to exist; and

computing a stabilized three-dimensional image using corrected phase offset images from the stable chain of phase offset images.

9. The method as claimed in claim 8 wherein the motion model accounts for global translational differences between successive phase offset images.

10. The method as claimed in claim 8 wherein the motion model accounts for local motion differences between successive phase offset images.

11. The method as claim in claim 8 wherein the motion model is an affine model or a projective model.

12. The method as claimed in claim 8 wherein the step of searching for a stable chain of phase offset images comprises testing ordered pairs of phase offset images in the bundle against a phase correlation threshold.

13. The method as claimed in claim 8 wherein the step of searching for a stable chain of phase offset images comprises collecting two or more ordered pairs in a connected list, where a connected list is defined as a set of at least two ordered pairs (x 1 ,y 1 ) and (x 2 ,y 2 ) in the list satisfying y 1 =x 2 and x 1 ≠y 2 .

14. The method as claimed in claim 8 wherein the step of searching for a stable chain of phase offset images further comprises the step of requiring an image bundle if a stable chain of phase offset images does not exist.

15. In a method for generating a three-dimensional image from a scannerless range imaging system of the type that computes range information from at least three images each incorporating a phase delay corresponding to the distance of objects in the scene from the range imaging system, the improvement wherein the method comprises the steps of:

acquiring a bundle of three or more images, whereby one or more of the images may be subject to unwanted movement with respect to another image;

searching for a stable chain of at least three images in the image bundle, where a stable chain is a collection of images that is found to exist where it is possible to characterize the unwanted movement between the images in relation to a motion model that is sensitive to a predetermined type of motion between the images;

if a stable chain of at least three phase offset images does not exist, requiring an image bundle until a stable chain is found to exist;

correcting for unwanted motion in the stable chain of images; and

computing a stabilized three-dimensional image using the images from the stable chain of phase offset images.

16. The method as claimed in claim 15 wherein the motion model accounts for translational motion between the images.

17. The method as claimed in claim 15 wherein the step of searching for a stable chain of phase offset images comprises testing ordered pairs of images in the bundle against a phase correlation threshold derived from the motion model.

18. A scannerless range imaging system for generating a stabilized three-dimensional image, said system comprising:

an illuminator for illuminating a scene with modulated illumination;

an image modulating component for receiving and modulating the modulated illumination reflected from the scene;

an image capture element for capturing images output by the image modulating component, whereby one or more of the images also includes image motion relative to another image, said captured images including a bundle of at least three phase offset images each incorporating a phase delay corresponding to the distance of objects in the scene from the illuminator, wherein each phase offset image also incorporates a phase offset unique for each image; and

a processor for processing the phase offset images captured by the image capture device, said processor performing the steps of:

searching for a stable chain of phase offset images in the image bundle, wherein a stable chain is a collection of images that is obtained by testing the phase offset images against a confidence measure that separates less severe correctable image motion from more severe image motion and then populating the stable chain only with those phase offset images that meet the confidence measure for correctable image motion;

correcting for the image motion in the stable chain of images if a stable chain of at least three phase offset images is found to exist; and

computing a stabilized three-dimensional image using the phase offset images from the stable chain of phase offset images.