Method and apparatus for determining the shape, distance and orientation of an object

A method for determining the three dimensional external contour of the cornea, comprising:

• creating an OCT en-face two-dimensional composite image of the cornea in a common image plane with a multiple delay OCT instrument employing a reference beam and an object beam, wherein the optical path length difference between the object and reference beams has a plurality of values produced by a differential delay element, whereby said composite image lying in said common image plane created by said multiple delay OCT instrument contains a series of superimposed two dimensional image contours of the cornea taken from planes at different depths determined by the optical path length differences;
• and
• computing the three dimensional external contour of said curved object from said two dimensional contours in said common image plane and the known optical path length differences at the corresponding planes at different depths.

A method of estimating the axial position of an object, comprising

• generating simultaneously a series of two dimensional image contours from planes at different image depths to create a two-dimensional composite en-face image in a common image plane using an OCT imaging instrument employing a reference beam and an object beam, wherein the optical path length difference between the object and reference beams has a plurality of values produced by a differential delay element, said planes at different depths having a known depth relationship determined by the differences in the optical path lengths at the different planes;
• and
• estimating the axial position of the object from the number of contours present in said composite image and the differential optical path differences between adjacent paths.

A method of obtaining geometrical information about an object, comprising:

• generating simultaneously a set of superimposed two dimensional image contours from planes at different depths to create a two-dimensional composite en-face image of the object in a common image plane using an OCT instrument employing a reference beam and an object beam, wherein the optical path length difference between the object and reference beams has a plurality of values produced by a differential delay element, said planes at different depths having a known depth relationship with each other;
• and
• computing the geometrical information about the object from said dimensional contours in said composite image and the known depth relationship between said planes at different depths.