METHOD AND APPARATUS FOR CALIBRATION OF STEREO-OPTICAL THREE-DIMENSIONAL SURFACE-MAPPING SYSTEM

• US 20140362186A1
• Filed: 01/04/2013
• Published: 12/11/2014
• Est. Priority Date: 01/04/2012
• Status: Active Grant

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Paulsen, Keith D., Roberts, David W., Ji, Songbai, Fan, Xiaoyao, Hartov, Alex
• Granted Patent: US 9,456,200 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G06T 2200/04 involving 3D image data
• CPC Class Codes: G06T 3/18 Image warping, e.g. rearranging pixels individually
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 2013/0074 Stereoscopic image analysis

Abstract

A system for, and method of, extracting a surface profile from a stereo pair of images obtained at an arbitrary setting S of an optical system, includes determining surface profile reconstruction parameters for images obtained with the optical system at a reference setting So of the optical system; determining warping parameters for a digital image processor for warping images obtained with the optical system at the arbitrary setting S into images corresponding to the reference setting So; obtaining the stereo pair of images from at least one camera of the optical system; warping the stereo pair of images into images corresponding to the reference setting So, and using the surface profile reconstruction parameters to determine the surface profile. In a particular embodiment, the surface profile is passed to a computer model of tissue deformation and used to determine an intra-surgery location of a tumor or other anatomic feature of tissue.

Claims

1-20. -20. (canceled)

21. A method of calibrating a system for extracting a surface profile from a stereo pair of images obtained at an arbitrary setting S of an optical system, comprising:

determining surface profile reconstruction parameters for images obtained with the optical system at a reference setting S0 of the optical system, the reference setting S0 being different from the arbitrary setting S;

determining warping parameters for a digital image processor for warping images obtained with the optical system at the arbitrary setting S into images corresponding to the reference setting S0.

22. The method of claim 21 wherein the settings S and S0 include at least a different configuration for magnification of the optical system.

23. The method of claim 22 further comprising recording surface profile reconstruction parameters for a plurality of reference settings recorded in a table.

24. The method of claim 23 further including recording warping parameters (DFPs) for warping images obtained with predetermined optical settings in the table, measuring a current set of optical parameters corresponding to the arbitrary setting S, and determining warping parameters for the arbitrary setting S by interpolation between the DFPs recorded in the table.

25. The method of claim 22 further including recording warping parameters (DFPs) for warping images obtained with predetermined optical settings in a table, measuring a current set of optical parameters corresponding to the arbitrary setting S, and determining warping parameters for the arbitrary setting S by interpolation between the DFPs recorded in the table.

26. The method of claim 21 wherein the settings S and S0 differ in at least configuration for focal length of the optical system.

27. The method of claim 21 wherein the machine readable instructions for determining warping parameters further comprise machine readable instructions for using images of a calibration phantom, the calibration phantom having reference marks, to determine the warping parameters.

28. The method of claim 27 wherein the reference marks of the calibration phantom are squares of randomly varied intensity.

32. A system adapted for extracting a surface profile comprising:

an adjustable optical system having a reference setting S₀ and at least one arbitrary setting S, the optical system having at least one camera for obtaining stereo image pairs, and wherein settings S and S0 include at least a magnification of the adjustable optical system;

an image processor coupled to receive stereo image pairs from the at least one camera of the optical system, further comprising a processor and a memory having recorded therein;

reconstruction parameters for determining a surface profile from images obtained with the optical system at the reference setting S₀;

machine readable instructions for using warping parameters to warp images obtained with the optical system at the arbitrary setting S into images corresponding to the reference setting S₀; and

machine readable instructions for using the reconstruction parameters to determine the surface profile.

33. The system of claim 32 wherein the settings S0 and S further comprise settings for a focal length of the optical system.

34. The system of claim 32 wherein the settings S0 and S further comprise settings for a camera angle of the optical system.

35. The system of claim 32, further comprising:

a library having recorded therein warping parameters DFPs for warping images obtained with predetermined optical settings,

an encoder adapted to measure a current set of optical parameters corresponding to the arbitrary setting S, the current set of optical parameters including at least a magnification,

and the memory configured with machine readable instructions for determining warping parameters for the arbitrary setting S by interpolation between the DFPs recorded in the library.

36. The system for extracting a surface profile of claim 35 further comprising machine readable instructions for using images of a phantom, the phantom having reference marks, to determine the warping parameters;

and wherein the images of the phantom are taken at settings S0 and S.

37. The system for extracting a surface profile of claim 35, the library further comprising 3D surface reconstruction parameters for at least two reference settings S1 and S2, and the system further including machine readable instructions for determining a reference setting S0 for an arbitrary setting S by selecting from the at least two reference settings S1 and S2 based upon at least magnification associated with setting S.

38. The system for extracting a surface profile of claim 35 further comprising an encoder for digitizing at least a focal-length setting, wherein the library of sets of warping parameters is further indexed by at least a digitized focal-length setting.

39. The system of claim 38 further comprising:

machine readable instructions for modeling deformation of the tissue to determine an intra-surgery location of an anatomic feature from the surface profile and preoperative images.

40. The system of claim 36 further comprising:

machine readable instructions for modeling deformation of the tissue to determine an intra-surgery location of an anatomic feature from the surface profile and preoperative images.

41. The system of claim 32 further comprising:

machine readable instructions for modeling deformation of the tissue to determine an intra-surgery location of an anatomic feature from the surface profile and preoperative images.