Apparatus and method for optically mapping front and back surface

Abstract

Apparatus for determining the topography of a surface of an ophthalmic object comprising a projection branch for projecting along a first optical axis a projected structured light pattern onto the surface of the ophthalmic object. The projected structured light pattern has light and dark regions that form an array comprised of horizontal features and non-horizontal edges, an algorithm in the computer establishes at least one projected virtual point for the projected structured light pattern by fitting a first function to a non-horizontal edge and fitting a second function to a horizontal feature to establish an intersection and the coordinates of the projected virtual point. An imaging branch provides a pattern image of the projected structured light pattern along a second optical axis angled with respect to the first optical axis of the projected structured light pattern. The algorithm in the computer establishes at least one image virtual point for the image pattern by fitting a first function to a non-horizontal edge and fitting a second function to a horizontal feature to establish an intersection and the coordinates of the image virtual point. The algorithm in the computer determines the elevation at one location on the surface of the ophthalmic object from the coordinates of the image virtual point and determines the elevations at additional locations on the surface of the ophthalmic object in the same manner as the elevation at said one location for ascertaining the topography of at least a portion of the surface of the ophthalmic object.