Sawtooth wave surface detection in 3D dental reconstruction system

1. A method for intraoral imaging comprising:

a) acquiring a plurality of structured light images from a region of interest and forming a range image that characterizes the surface contour of the region of interest according to the acquired structured light images;

b) processing at least one row of pixels in the range image by:

(i) selecting a segment of the row;

(ii) computing residual noise in the selected segment;

(iii) generating a template for the segment, wherein the template is characteristic of an imaging artifact related to motion;

(iv) computing a similarity factor according to correlation between frequency-domain transforms of the template and computed residual noise;

(v) comparing the computed similarity factor against a threshold to identify an image artifact;

and

c) reporting the image artifact or excessive motion.

2. The method of claim 1 wherein the image artifact relates to a sawtooth or corrugated surface effect.

3. The method of claim 1 wherein the image artifact results from unintended motion of a scanning apparatus.

4. The method of claim 1 further comprising smoothing the selected segment.

5. The method of claim 1 wherein the frequency-domain transform is a Fourier transform.

6. The method of claim 1 wherein the structured light images use a pattern of parallel lines.

7. The method of claim 1 wherein selecting comprises identifying a smooth continuous segment of the row.

8. The method of claim 1 wherein computing the similarity factor uses the standard deviation for the row.

9. The method of claim 1 wherein the structured light images show one or more teeth.

10. The method of claim 1 wherein the segment contains a plurality of sawtooth surface effects.

11. A method for intraoral imaging comprising:

a) acquiring a plurality of structured light images from a region of interest and forming a range image that characterizes the surface contour of the region of interest according to the acquired structured light images;

b) processing at least one row of pixels in the range image by:

(i) selecting a smoothly continuous segment of the row;

(ii) smoothing the selected segment;

(iii) computing residual noise in the smoothed, selected segment;

(iv) generating a template for the segment, wherein the template is characteristic of an imaging artifact related to motion;

(v) computing a similarity factor according to correlation between Fourier transforms of the template and computed residual noise;

(vi) comparing the computed similarity factor against a threshold to identify an image artifact; and

c) reporting the image artifact or excessive motion.

12. An imaging apparatus for intraoral imaging comprising:

a) a scanner that acquires a plurality of images of a light pattern repeatedly projected onto a surface;

b) a logic processor that executes programmed instructions for forming a range image from the acquired plurality of light pattern images and processes at least one row of pixels in the range image by:

(i) computing residual noise in the row;

(ii) generating a template for at least a segment of the row, wherein the template is characteristic of an imaging artifact related to motion;

(iii) computing a similarity factor according to correlation between Fourier transforms of the template and computed residual noise;

(iv) comparing the computed similarity factor against a threshold to identify an image artifact; and

c) an audible or visual indicator in signal communication with the logic processor and energizable to report the image artifact or excessive motion.