Camera calibration using fiducial markers on surgical tools

Inventors

Nir, Tal • ALPERT, Lior

Assignees

Asensus Surgical Europe SARL • Asensus Surgical Europe SARL Luxembourg

Abstract

Calibration of parameters of an endoscopic or laparoscopic camera is conducted while the camera is in use capturing images of a surgical procedure at a surgical site. The surgical procedure is performed using a surgical instrument marked with a fiducial pattern. A processor receives image data from images captured by the camera and uses machine vision to detect points of the pattern, and carries out an optimization to determine the 3D pose of the surgical instrument relative to the camera and the camera parameters.

Core Innovation

The invention provides an on-the-fly camera calibration approach for endoscopic or laparoscopic surgical procedures by using a surgical instrument that includes an elongate shaft with a fiducial calibration pattern. The fiducial calibration pattern is positioned within a body cavity so that it is visible to a mono or stereo endoscopic camera capturing images from within the body cavity during a surgical procedure. The camera captures a plurality of images of the marked surgical instrument, and processing uses image fiducials together with known fiducials geometry to estimate camera parameters.

In one aspect, the fiducial calibration pattern is disposed on the elongate shaft and includes a known geometric pattern, such as checkerboard fiducials made from ordered corners. The fiducial calibration pattern can extend around the shaft circumference to provide 360-degree circumferential fiducial coverage. Using the locations of fiducial points in the plurality of images and the known geometry of the fiducial calibration pattern, intrinsic camera parameters are estimated for a stereo endoscopic camera used at the surgical site.

In another aspect, the estimation supports use in a surgical system that includes at least one processor executing algorithms to receive images from the stereo endoscopic camera while the camera distal tip is positioned within the body cavity. Based on the location of scene points in the fiducial calibration pattern across the captured images and the known geometry of the fiducial calibration pattern, the stereo endoscopic camera parameters are estimated. The calibration is described as enabling distortion correction, stereo 3D reconstruction, and surgical site 3D measurements, and as avoiding a dedicated pre-surgery calibration stage.

Claims Coverage

The independent claims cover three inventive areas: a surgical instrument with a fiducial calibration pattern positioned for estimating intrinsic parameters of a stereo endoscopic camera, a method of calibrating a camera during surgery using images of a fiducial calibration pattern with known geometry, and a surgical system that estimates stereo endoscopic camera parameters by processing images of the fiducial calibration pattern captured within a body cavity. The core inventive features focus on placing a fiducial calibration pattern on an elongate shaft inside the body cavity, using the camera to capture a plurality of images of that pattern, and estimating camera parameters from the image fiducials and known fiducial geometry.

Overall, the claim coverage emphasizes calibrating a stereo endoscopic camera during surgery using an instrument-carried fiducial calibration pattern within a body cavity, where camera parameters are estimated from the locations of image fiducials in a plurality of images and known fiducials geometry.

Stated Advantages

Documented Applications