| 摘要 |
A focusing apparatus is used to adjust the relative location of an object (14, 16) and a focal point in, for example, the preparation of an integrated semiconductor circuit (IC). The focusing apparatus adjusts the relative location in response to the intensity of a light beam reflected from the object (14, 16). This response varies with the orientation of the beam and any surface structure on the object (14, 16) and, to overcome this, the apparatus includes a plurality of opposed photo emitters (41) and photo detectors (42) arranged around the object (14, 16) so that the intensity of a plurality of light beams having diferent orientations to the surface structure of the object (14, 16) are monitored simultaneously. |
