Patent ID: 7433128

Claim:
An adaptive light-path surface tilt sensing configuration that can be used to identify a ray bundle that is projected along a direction normal to a point on a workpiece surface, the tilt sensing configuration comprising: an objective lens; and an illumination and detector portion including elements comprising a light source, a collimating lens, a beamsplitter, a ray bundle position control portion comprising an aperture, and a photodetector configuration, wherein: a portion of the tilt sensing configuration forms a ray bundle alignment sensing arrangement; and the tilt sensing configuration is configured such that: an illuminating beam from the light source is output via an arrangement of the collimating lens, the beamsplitter and the aperture of the ray bundle position control portion to provide a collimated projected ray bundle at a projected ray handle position; a portion of the objective lens inputs the projected ray handle and projects the projected ray bundle such that it is focused at a point on the workpiece surface along a direction of incidence; the objective lens inputs a reflected ray bundle from the workpiece surface and outputs the reflected ray bundle to the ray bundle alignment sensing arrangement; the ray bundle alignment sensing arrangement outputs a measurement signal that is usable to determine a degree of alignment between the projected ray bundle and the reflected ray bundle, the degree of alignment between the projected ray bundle and the reflected ray bundle corresponding to a degree of alignment between the projected ray bundle and a surface normal at the point on the workpiece surface; when the measurement signal indicates that a projected ray bundle and a reflected ray bundle are aligned, then that projected ray bundle is identified as the ray bundle that is projected along a direction normal to the point on the workpiece surface, and a corresponding state of the ray bundle position control portion is indicative of the workpiece surface tilt direction at the point on the workpiece surface.