Laser probe optical system

The laser beam from the optical system reflects on a workpiece surface and its scattering light is captured by the objective to form a laser spot on the autofocus (AF) sensor. The laser spot is positioned at the center of the AF sensor when the workpiece surface is in focus. The laser spot position displaces upward or downward when the workpiece surface is out of focus. The AF sensor detects the laser spot displacement and feeds back the information to the AF mechanism in order to adjust the objective back to the in-focus position. The workpiece is controlled in three axes (X, Y, and θ) and the laser probe is controlled in two axes (AF and Z) axes. This control mechanism offers profile measurements of various kinds of workpieces by obtaining each coordinate value at each in-focus position.