Recovering perspective distortions

Patent metadata

Field	Value
Publication number	US-11460931-B2
Application number	US-201817056442-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Oct 31, 2018
Publication date	Oct 4, 2022
Grant date	Oct 4, 2022

Abstract

A method for recovering perspective distortion of a coded dot pattern on a surface, comprises generating a stereo-pair of images of a portion of the coded dot pattern, the stereo-pair of images comprising an overlap region comprising a subset of dots of the coded dot pattern that are common to the stereo-pair of images, selecting, in one image of the stereo-pair of images, a focus pattern from the subset of dots, determining a set of potential matches for the focus pattern in the other image of the stereo-pair of images, for each potential match, determining a set of additional dots of the coded dot pattern consistent with a single plane, and selecting a single plane with the highest number of consistent matched dots.

First claim

The invention claimed is:

1. A method for recovering perspective distortion of a coded dot pattern on a surface resulting from a digital stylus being located at a non-right angle to the surface, comprising:
capturing a stereo-pair of images of a portion of the coded dot pattern using an image sensor of the digital stylus, the stereo-pair of images captured from opposing sides of the digital stylus, the stereo-pair of images comprising an overlap region comprising a subset of dots of the coded dot pattern that are within both of the stereo-pair of images;
selecting, in one image of the stereo-pair of images, a focus pattern from the subset of dots within the overlap region within both of the stereo-pair of images;
determining a set of potential matches for the focus pattern in the other image of the stereo-pair of images;
for each potential match, determining, in the other image of the stereo-pair of images, a set of additional dots of the coded dot pattern consistent with a single plane; and
selecting the single plane of the potential match with a highest number of additional dots to recover the perspective distortion of the coded dot pattern on the surface resulting from the digital stylus being located at the non-right angle to the surface.

2. The method of claim 1 , wherein determining the set of potential matches for the focus pattern comprises:
using a set of dots within a predetermined region around the focus pattern.

3. The method of claim 2 , wherein determining the set of potential matches for the focus pattern further comprises:
iteratively growing the predetermined region to encompass an increasing neighborhood of dots.

4. The method of claim 1 , wherein determining the set of potential matches for the focus pattern in the other image of the stereo-pair of images comprises:
selecting multiple dots falling along a horizontal epipolar line projected, in the other image, at a vertical position corresponding to the vertical position of the focus pattern.

5. A digital stylus comprising:
an image sensor to capture a stereo-pair of images of a portion of a coded pattern on a surface; the stereo-pair of images captured from opposing sides of the digital stylus, the stereo-pair of images comprising an overlap region comprising a subset of dots of the coded dot pattern that are within both of the stereo-pair of images; and
a processor to:
select, in one image of the stereo-pair of images, a focus pattern from the subset of dots within the overlap region within both of the stereo-pair of images;
determine, for each of a set of potential matches for the focus pattern in the other image of the stereo-pair of images, a set of additional dots of the coded pattern in the other image of the stereo-pair of images that are consistent with a single plane and based around a set of potential matches for the focus pattern; and
select the single plane of the potential match with a highest number of additional dots to recover perspective distortion of the coded dot pattern on the surface resulting from the digital stylus being located at a non-right angle to the surface.

6. The digital stylus of claim 5 , wherein the image sensor comprises a single image sensor to capture the stereo-pair of images of the portion.

7. The digital stylus of claim 5 , wherein the image sensor structure comprises a pair of image sensors to capture respective ones of the stereo-pair images of the portion.

8. The digital stylus of claim 7 , wherein the pair of images sensors are disposed on generally opposite sides of the digital stylus.

9. The digital stylus of claim 5 , further comprising a source of near infra-red radiation to illuminate the surface.

10. The digital stylus apparatus as claimed in of claim 6 , the processor to use two overlapping regions of the image sensor to capture the stereo-pair of images.

11. The digital stylus of claim 5 , further comprising a prism or semi-reflective mirror to reflect a portion of the coded pattern on the surface to the image sensor structure.

12. The digital stylus of claim 5 , further comprising a nib, the processor to select the focus pattern from a region of the coded pattern in a vicinity of the nib.

13. A non-transitory machine-readable storage medium encoded with instructions executable by a processor to:
capture a stereo-pair of images of a portion of a coded dot pattern on a surface using an image sensor of a digital stylus located at a non-right angle to the surface, the stereo-pair of images captured from opposing sides of the digital stylus, the stereo-pair of images comprising an overlap region comprising a subset of dots of the coded dot pattern that are within both of the stereo-pair of images;
select, in one image of the stereo-pair of images, a focus pattern from the subset of dots within the overlap region within both of the stereo-pair of images;
generate a set of potential matches for the focus pattern in the other image of the stereo-pair of images;
for each potential match, determine, in the other image of the stereo-pair of images, a set of additional dots of the coded dot pattern consistent with a single plane; and
select the single plane of the potential match with a highest number of additional dots to recover perspective distortion of the coded dot pattern on the surface resulting from the digital stylus being located at the non-right angle to the surface.

14. The non-transitory machine-readable storage medium of claim 13 , wherein the instructions are executable by the processor to generate the set of potential matches for the focus pattern in the other image by:
iteratively enlarging a predetermined region around the focus pattern to encompass an increasing neighborhood of dots.

15. The non-transitory machine-readable storage medium of claim 13 , wherein the instructions are executable by the processor to generate the set of potential matches for the focus pattern in the other image by:
selecting multiple dots falling along a horizontal epipolar line projected, in the other image, at a vertical position corresponding to the vertical position of the focus pattern.

16. The method of claim 1 , wherein the digital stylus is a digital pen or an opto-electronic pen.

17. The digital stylus of claim 5 , wherein the digital stylus is a digital pen or an opto-electronic pen.

18. The non-transitory machine-readable storage medium of claim 13 , wherein the digital stylus is a digital pen or an opto-electronic pen.

Assignees

• Hewlett Packard Development Co

Inventors

• Pollard Stephen

Classifications

• G06F3/0317 Primary

  in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface · CPC title

• G06T7/593 Primary

  from stereo images · CPC title

• H04N23/56

  provided with illuminating means · CPC title

• G06F18/22

  Matching criteria, e.g. proximity measures · CPC title

• H04N13/207

  using a single two-dimensional [2D] image sensor · CPC title