Calibration method for optical see-through display and calibration system

A calibration system configured to calibrate an optical see-through display, wherein the calibration system comprises:

• an image sensing device, fixed at a standard position of an eye of a user seeing the optical see-through display, wherein the image sensing device is configured to photograph a virtual image displayed by the optical see-through display and an image of a real object in an environment;
• and
• a controller, coupled to the image sensing device and the optical see-through display, wherein the controller is configured to:
• photograph a virtual calibration pattern displayed by the optical see-through display by commanding the image sensing device, and obtain a coordinate value of an image of a plurality of first feature points of the virtual calibration pattern;
• calculate a projection homography matrix for transforming an image plane of the image sensing device to an image plane of the optical see-through display by using the coordinate values of the image of the plurality of first feature points and coordinate values of the first feature points of the virtual calibration pattern;
• turn off the optical see-through display and photograph a plurality of images of a calibration pattern of the real object at different angles by using the image sensing device, wherein the calibration pattern of the real object comprises a plurality of second feature points;
• calculate intrinsic parameters of the image sensing device and extrinsic parameters between the image sensing device and the plurality of calibration patterns of the real object by using coordinates of the plurality of second feature points in the plurality of images of the calibration pattern of the real object and the plurality of second feature points on the calibration pattern of the real object;
• transform the coordinates of the plurality of second feature points in the plurality of images of the calibration pattern of the real object to coordinates of projection points of the image plane of the optical see-through display by using the projection homography matrix;
• calculate intrinsic parameters of a virtual camera of the optical see-through display and extrinsic parameters between the virtual camera and the plurality of calibrations patterns of the real object by using the coordinates of the plurality of projection points transformed to the image plane of the optical see-through display from the plurality of images of the calibration pattern of the real object;
• and
• calculate extrinsic parameters between the image sensing device and the virtual camera by using the extrinsic parameters between the image sensing device and the plurality of calibration patterns of the real object and the extrinsic parameters between the virtual camera and the plurality of calibration patterns of the real object.