APPARATUS AND METHOD FOR ADJUSTING THE FOCUS AUTOMATICALLY

摘要

An auto focusing apparatus and a method thereof are provided, which perform the auto focusing by flexibly coping with the diffuse reflection problem and the pattern influence generated by the inspection specimen. An auto focusing apparatus(120) comprises the laser beam output part(10), the diffraction grating(40), the beam splitter(60), the objective lens(70), cylindrical lenses, the convex lens(100), the optical detector(110), arithmetic and logic unit, the storage media, the control device, and the drive motor. In the laser beam output part, the circular laser beam controlling the quantity of light is outputted. The diffraction grating radially divides the laser into a plurality of rays. The beam splitter makes the divided light ray incident in the specimen(80). The convex lens gathers the light passing through the cylindrical lens to the domain of the optical detector. The drive motor is driven according to the control signal by the control device.